What are the key differences between living and nonliving organisms?

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Quick Answer

The main difference between living and non-living things is that a living organism is or was once alive, whereas a non-living thing has never been alive. Non-living is not the same as being dead because non-living things were never alive and therefore cannot die.

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According to biologists, these are the signs of life: a highly organized and complex structure; the maintenance of a chemical composition distinct from their surroundings; the ability to take in, transform and use energy from their environment; a response to outside stimuli; the ability to reproduce; and the capacity to grow and develop.

All plants and animals are living organisms. Not all living organisms move in an obvious way. Some, such as trees and coral, move in small increments, while others, such as people and animals, move much more clearly.

Not all living organisms reproduce in the same way either. A fungus reproduces asexually (without a partner) via spores that migrate and grow new fungi. Earthworms are hermaphroditic, however, which means that each earthworm biologically has male and female parts but needs a partner to fertilize an egg to make new earthworms.

Nonliving things do not have any of the signs of life mentioned above. Usually, nonliving things, such as pots and pans or silverware, are made of plastics or metals. On the other hand, objects made from wood or natural fibers, including cotton and yarn, are viewed as "living" due to the fact that they were once alive. Stones, rocks, sand and water are considered non-living because they were never alive, but each of these may have living organisms, such as micro-organisms, inside them.